[R-meta] Help with variance stabilizing transformation methods in Metafor

Todor Krastev dr.todor.krastev at gmail.com
Wed Jan 17 22:54:27 CET 2018

Thank you for the tip Wolfgang!
Silly of me not to have thought of that...

Then I guess you have helped me out with everything!



On 17 January 2018 at 22:28, Viechtbauer Wolfgang (SP) <
wolfgang.viechtbauer at maastrichtuniversity.nl> wrote:

> Just divide the person times by 100 before the analysis. See:
> http://www.metafor-project.org/doku.php/analyses:
> stijnen2010#poisson-normal_model_for_the_meta-analysis_of_incidence_rates
> Then the forest plot will automatically show you rates per 100 pt yrs.
> Best,
> Wolfgang
> -----Original Message-----
> From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-
> bounces at r-project.org] On Behalf Of Todor Krastev
> Sent: Wednesday, 17 January, 2018 21:34
> To: Guido Schwarzer
> Cc: r-sig-meta-analysis at r-project.org
> Subject: Re: [R-meta] Help with variance stabilizing transformation
> methods in Metafor
> Dear Guido,
> Thank you for your prompt reply!
> It took me some time to fix it and react to your email, but I did manage
> in the end to fit the Poisson-normal model as described in Stijnen (2010),
> which led to much more logical effect estimates in my meta-analysis.
> I didnt quite succeed to work it out with the Meta package due to some
> errors in the GLMM function and changed the decimal places manually (x100)
> in Metafor to obtain the numbers as %.
> As you can see in the attachment, I also obtained the 0.73 value with
> Poisson (see attachment).
> Also, maybe Wolfgang knows an simpler way to transform Forest plot values
> in Metafor also to achieve numbers per 100 pt yrs?
> I also checked out the Meta package and does look super neat in the way it
> presents the individual study estimates in grey colour (makes the 95%CI
> visible in large studies) and also automatically gives you the weighing of
> studies and the measure of heterogeneity (all these I had to add manually).
> It definitely got my attention and I shall try it out for my next project.
> Thank you once again for your great help!
> Regards,
> Todor

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